Numerical Simulation Of Operating Period Failure Probability Of Depleted Gas Storage Underground Gas Storage

The depleted gas reservoir is a kind of gas reservoir which is the most widely used and longest used gas reservoir in the world.With the rapid development of natural gas industry in China,the demand for underground gas storage becomes more and more urgent.According to the forecast,by 2020,the gas demand of the national underground gas storage will exceed 500×108m3,and the gas volume of 60%-70%will be obtained through the reconstruction of depleted gas reservoirs.Therefore,it is of great significance for the construction of underground gas storage in China to seize the key to rebuild the underground gas storages by depleted gas reservoirs,and to build and operate the underground gas storages with depleted gas reservoirs.In the past 30 years,the world within the scope of the depleted oil and gas reservoirs of underground gas storage has several accidents,sounded the alarm for China's underground gas storage.operation;but at this stage of the depleted oil and gas reservoirs of underground gas storage failure factors of reason and corresponding effects are still lacking,the failure probability of operation simulation the stage is not clear.Therefore,it is imminent to study the failure causes of depleted gas storage underground gas storage,understand the failure factors of underground gas storage,and simulate the failure probability during the operation of gas storage,which will have a significant impact on China's future economic and livelihood issues.When analyzing the failure probability of reservoir operation period,the main method is based on the finite element method,and the accuracy of calculation failure probability is improved based on Monte Carlo method.In this paper,a single cavity numerical calculation model is established,and the failure probability analysis is carried out.The main contents are summarized briefly:(1)a large number of references were consulted,and the reasons for the failure of the depleted gas storage underground gas reservoir and the influencing factors of its stability were summarized on the basis of experimental data and case statistics.The mechanical properties,the shape of the storage chamber,the operation pressure of the storage chamber,the surrounding rock and the spacing of the storage chamber will affect the stability of the depleted gas storage underground gas storage.The stability of edge water storage cavity caused little effect;should be considered the geological conditions of reservoir and cavity shape in the database,the use of depleted gas reservoir construction of underground reservoir to choose class ellipsoid cavity to reduce cavity volume shrinkage rate,prolong storage life.When using more than two storage cavities to construct gas storage group,the reasonable choice of cavity spacing is suggested to be 2 times the maximum diameter of the storage cavity D.(2)the establishment of a single cavity numerical calculation model,discusses the main failure modes of structural system,the Mohr Coulomb criterion as failure criterion;failure criterion based on the failure probability of the largest unit,on the basis of the Monte Carlo algorithm,a preliminary calculation of system failure probability.Single cavity reservoir calculation results show that when the gas pressure is low,the failure mode for the middle part of the cavity shear failure,as gas pressure increases,the failure probability increases,when the pressure is higher than a certain value,the failure probability increases,the tensile failure and therefore strictly control pressure in gas reservoir engineering to deal with.